@@ -718,7 +718,7 @@ dmg_co_preadv(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
BDRVDMGState *s = bs->opaque;
uint64_t sector_num = offset >> BDRV_SECTOR_BITS;
int nb_sectors = bytes >> BDRV_SECTOR_BITS;
- int ret, i;
+ int ret, i = 0;
DMGReadState *drs = s->drs;
assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
@@ -726,8 +726,7 @@ dmg_co_preadv(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
qemu_co_mutex_lock(&s->lock);
- for (i = 0; i < nb_sectors; i++) {
- uint32_t sector_offset_in_chunk;
+ while (i < nb_sectors) {
void *data;
if (dmg_read_chunk(bs, sector_num + i, drs) != 0) {
@@ -738,12 +737,20 @@ dmg_co_preadv(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
* s->uncompressed_chunk may be too small to cover the large all-zeroes
* section. dmg_read_chunk is called to find s->current_chunk */
if (s->types[s->current_chunk] == 2) { /* all zeroes block entry */
- qemu_iovec_memset(qiov, i * 512, 0, 512);
- continue;
+ qemu_iovec_memset(qiov, i * 512, 0,
+ 512 * drs->sectors_read);
+ goto increment;
+ }
+
+ if (drs->saved_next_in == NULL) {
+ data = s->uncompressed_chunk + drs->sector_offset_in_chunk * 512;
+ } else {
+ data = s->uncompressed_chunk;
}
- sector_offset_in_chunk = sector_num + i - s->sectors[s->current_chunk];
- data = s->uncompressed_chunk + sector_offset_in_chunk * 512;
- qemu_iovec_from_buf(qiov, i * 512, data, 512);
+ qemu_iovec_from_buf(qiov, i * 512, data, drs->sectors_read * 512);
+
+increment:
+ i += drs->sectors_read;
}
ret = 0;
At the moment, dmg_co_preadv() reads one sector at a time. Make it read multiple sectors at a time depending on the number of sectors stored in "drs->sectors_read". This does not provide any significant optimization in the I/O process of DMG but is still a nicer way. Adjust the 'data' variable depending on our cached access point situation to align our read requests appropriately. Signed-off-by: Ashijeet Acharya <ashijeetacharya@gmail.com> --- block/dmg.c | 23 +++++++++++++++-------- 1 file changed, 15 insertions(+), 8 deletions(-)